A vacuum cleaner typically comprises a main body containing dirt and dust separating apparatus, a floor tool connected to the main body and having a suction opening, and a motor-driven fan unit for drawing dirt-bearing air through the suction opening. The suction opening is directed downwardly to face the floor surface to be cleaned. The dirt-bearing air is conveyed to the separating apparatus so that dirt and dust can be separated from the air before the air is expelled to the atmosphere. The separating apparatus can take the form of a filter, a filter bag or, as is known, a cyclonic arrangement. The present invention is not concerned with the nature of the separating apparatus and is therefore applicable to vacuum cleaners utilizing any of the above arrangements or another suitable separating apparatus.
A driven agitator, usually in the form of a brush bar, is supported in the floor tool so as to protrude by a small extent from the suction opening. The brush bar is activated mainly when the vacuum cleaner is used to clean carpeted surfaces. The brush bar comprises an elongate cylindrical core bearing bristles which extend radially outward from the core.
Rotation of the brush bar may be driven by an electric motor powered by a power supply derived from the main body of the cleaner, or by an air turbine assembly driven by an air flow into the floor tool. The rotation of the brush bar causes the bristles to sweep along the surface of the carpet to be cleaned to loosen dirt and dust, and pick up debris. The suction of air generated by the fan unit of the vacuum cleaner causes air to flow underneath the floor tool and around the brush bar to help lift the dirt and dust from the surface of the carpet and then carry it from the suction opening through the floor tool towards the separating apparatus.
The air flow into the suction opening may be varied by a user during a cleaning operation. For example, it is known to provide a bleed valve on a wand to which the floor tool is connected to allow ambient air to be admitted into the air flow passing from the floor tool to the separating apparatus. When the bleed valve is opened by the user there is a decrease in the rate at which air enters the floor tool through the suction opening, and so there is a decrease in the level of suction at the floor tool. This can enable items which may have become stuck within the floor tool to be dislodged, and can enable a user to clean relatively delicate items, such as curtains or other fabrics, without the fabric becoming lodged within the floor tool.